Systems are used to convert solar energy into other forms of energy which can be used or stored. These systems utilize a solar collector which collects the solar radiation and converts the solar energy therein into a useable form of energy such as heat. Solar collectors of the flat plate type have been utilized in low energy applications such as heating water, generating low pressure steam, and supplementing air conditioning and heating systems and the like. Flat plate collectors do not focus the sun's radiation and have limited applicability. Another type of collector is generically called a concentrating collector. These collectors function to collect the sun's radiation energy and focus or concentrate the energy in a particular area. These concentrating collectors can be designed to operate at high temperatures with reasonable flow rates, thus substantially increasing the versatility of systems incorporating these collectors over that of flat plate collectors.
One type of concentrating collector is known as the parabolic trough collector. This type collector uses an elongated reflective trough having a parabolic cross-section to concentrate the sun's radiation along a focal line extending through the focal points of the parabolic elements of the trough. A conduit can be positioned along this focal line and a heat transfer liquid can be circulated through the conduit. The liquid will be heated by the sun's energy. Satisfactory flow rates at high temperatures can be obtained from these collectors. It has also been found that by use of tracking systems these parabolic trough collectors can become extremely efficient as they follow the movement of the sun. Designs for these collectors can be found in the prior art such as is disclosed in my prior application Ser. No. 853,213 filed Nov. 21, 1977, now U.S. Pat. No. 4,240,406.
Trough type collectors are becoming accepted as the most efficient and versatile means of generating energy from solar radiation. As solar systems are used to satisfy larger energy requirements, the systems incorporating the collectors become physically larger. Presently, systems using a plurality of collectors whose aggregate collector surface approaches a thousand square meters are in use. These systems have been used as solar collectors in systems for irrigation pumping; solar heating and air conditioning; steam generation for raw crude oil processing and other industrial applications; generating electrical energy directly from photovoltec cells; and powering small power plants.
Conventionally, trough type solar collectors have been supported on an axis extending parallel to the focus line. These collectors are journaled by bearings to rotate to point the reflector surface directly toward the sun. Typically, two pylons or supports are rigidly mounted to support the individual collectors in a rotatable position elevated from the surface of the ground.
To achieve the collector areas required for some applications it has been conventional to utilize collectors of a size approximately six meters long and approximately two and one-half meters wide. A plurality of these collectors are mounted in an array or field. In some applications as many as six collectors are mounted on a common axis and are mechanically connected together so that all six collectors may be rotated to track the sun as a single unit. A plurality of these rows are utilized to obtain the total collector area required for the particular application. Attempts have been made to lower the per unit area cost of support equipment such as the tracking units for each row by increasing the length of each row. The benefit of these attempts have been offset by the torsional flexibility added to the system by increasing the overall length of an interconnected row of collectors and thus increasing the length to width ratio. This flexibility creates problems in focusing the collectors and in preventing damage to the system during high winds. Stiffening the individual collector units themselves suffers from the disadvantage of substantially increasing the manufacturing costs. It was also believed in the industry that attempts to increase the width of the collector substantially beyond the two and one-half meter range could not be achieved due to manufacturing, structural, transportation and handling problems caused by a unit of such a size. Thus, the solar industry is faced with a problem of providing an inexpensive and efficient solar collector to satisfy large energy applications.
One attempt to solve this problem is proposed by a Mr. Caplan in his U.S. Pat. No. 3,959,056. To attack the problem, Mr. Caplan proposes in his patent to use a honeycomb construction for a concentrating type collector. Mr. Caplan suggested the provision of fabricating apparatus mounted on semitrailer trucks. The trucks could be positioned at the site to produce collectors having a width in the area of sixteen feet and a length in the area of forty feet. It is inherent in Mr. Caplan's system that the efficiency of a permanent factory and personnel would be abandoned and that an expensive honeycomb material construction would be necessary. The system proposed by Mr. Caplan apparently is as a result of the inventor's (and solar industries') belief that large width focusing solar collectors could not be manufactured at a fixed plant because of the problems attendant to manufacturing, shipping, and installation of these large modules.
Even though this great need for collectors of substantial width is recognized in the industry, no one to Applicant's knowledge has proposed an economical system for manufacturing and installing solar collectors of extended width.